There are many satellites presently in geosynchronous orbit to facilitate communications with and surveillance of specific land masses. It is important to form the beams to the shape of the geographic target so as not to waste the gain of the antenna being used. Contoured beam antenna systems are used on these satellites to conform the beam to the target.
Antenna used for surveillance or communications satellites need to be shaped to provide a target pattern which conforms as closely as possible to the shape of the target location. This maximizes the power directed at the target and increases the response of the associated system. In order to accommodate multiple targets, multiple antenna radiation patterns must be generated. Prior art systems utilized a reflector antenna with a feed array which is connected to a power source through a variable power driver beam forming network. By proper excitation of the feed array, the antenna radiation pattern can be changed. The problem, however, is in the beam forming network, which is a major source of passive intermodulation interference. The beam forming network also adds considerable weight and expanse to the system.
It is the purpose of this invention to generate multiple contoured beams utilizing a single antenna and feed.